Danny Flood's Hack Sleep is a guide for enhancing sleep quality and tackling insomnia. The book explains the science of sleep and details the roles of hormones such as cortisol, adenosine, melatonin, and serotonin. It also examines circadian and ultradian rhythms, highlighting the significance of light exposure and regulating body temperature.

Flood provides practical hacks to improve sleep, including napping techniques, meditation, self-hypnosis, and breathing exercises. It also delves into lucid dreaming and includes a bonus chapter from Daywistle offering advice for those facing severe insomnia. Flood incorporates personal anecdotes and research to propose actionable strategies for achieving restful sleep.